1. Field of Invention
The invention relates to a technology regarding a method of supplying paint into a paint cartridge. More concretely, the invention relates to a technology regarding a paint supply method that is able to economically and certainly reduce the paint loss in conjunction with a paint cartridge that is detachably attached to an electrostatic painting machine, without requiring the provision of a mechanical shutting-off mechanism or the like.
2. Description of Related Art
Generally, the painting of bodies of motor vehicles and the like, due to its requirement for high painting quality, employs electrostatic painting machines that are excellent in the efficiency of adhesion of paint to painting surfaces, the smoothness of paint films after the painting process, etc. A widely known example of the electrostatic painting machines is a rotary atomizing head type painting machine. The rotary atomizing head type painting machine is equipped with a rotary atomizing head for atomizing a water base paint, a plurality of paint cartridges that are filled with paints of different colors, etc. To perform painting of an object to be painted, a paint cartridge filled with a paint of a designated color is selected. Then, the paint filled in the paint cartridge is jetted out via rotary atomizing heads, so that paint particles are atomized, and accomplish the painting. When the paint in the paint cartridge runs out, the paint cartridge is attached to a paint filling apparatus (paint supply apparatus), and is thereby supplied with the paint again. Thus, the rotary atomizing head type painting machine becomes able to carry out the painting again.
As for the paint supply apparatus for supplying paint into a paint cartridge that has become empty, various constructions have been proposed. A known example thereof is a paint supply apparatus that is equipped with a filling valve.
With reference to FIGS. 4A and 4B, a general construction of a filling valve 1 will be described. Inside the filling valve 1, there are provided a paint supply channel 3 that is detachably linked in communication with a supply portion 11 that leads to the inside of a paint cartridge 10, a trigger valve 9 that functions as an open-close valve of the paint supply channel 3 at the site of linkage in communication between the paint supply channel 3 and the supply portion 11, etc. In the vicinity of the trigger valve 9, a cleaning liquid supply channel 7 and a waste liquid discharge channel 8 are linked in communication with the paint supply channel 3. Via the cleaning liquid supply channel 7, a cleaning liquid for cleaning the site of linkage in communication between the supply portion 11 and the paint supply channel 3 as well as compressed air and the like are supplied to the vicinity of the site of linkage. Besides, the waste liquid having been used to clean the vicinity of the linkage site is discharged to the outside of the filling valve 1 via the waste liquid discharge channel 8.
In a paint supply method for the paint cartridge 10 of a comparative example which uses the foregoing filling valve 1, when paint is to be supplied from the filling valve 1 into the paint cartridge 10, the trigger valve 9 is moved (in the direction of an arrow Q1 shown in FIG. 4A) to change the paint supply channel 3 into an “open” state. Then, the paint supply channel 3 becomes linked in communication with the cleaning liquid supply channel 7 and the waste liquid discharge channel 8 as well as with the supply portion 11. As a result, as shown in FIG. 4B, a part of paint 51 that flows inside the paint supply channel 3 flows out into the cleaning liquid supply channel 7 and the waste liquid discharge channel 8, so that the part of the paint 51 compresses the air remaining in the two channels 7 and 8, and thus fills substantially the entire spaces in the two channels 7 and 8. The paint 51 filling the cleaning liquid supply channel 7 and the waste liquid discharge channel 8 is washed off by the cleaning liquid and is discharged to the outside of the filling valve 1 at the time of changing the paint color that is supplied through the filling valve 1. The thus-discharged amount of the paint 51 is not fed back into the paint cartridge 10, but is discarded as a paint loss.
In order to minimize the paint loss that occurs, at the time of supplying paint into a paint cartridge, there have been proposed technologies as shown in Japanese Patent Application Publication No. 2000-176328 (JP-A-2000-176328), Japanese Patent Application Publication No. 2008-212869 (JP-A-2008-212869), and Japanese Patent Application Publication No. 2009-56382 (JP-A-2009-56382).
That is, Japanese Patent Application Publication No. 2000-176328 (JP-A-2000-176328) proposes a paint filling apparatus that fills a paint into a paint cartridge that is constructed of a cylinder that is to be filled with the paint and a feed tube that extends in the direction of a center axis of the cylinder. Specifically, the disclosed technology relates to an apparatus for filling a paint into a cartridge which has: a feed tube insert hole to insert the feed tube through is provided extending in the direction of an axis of the feed tube; a filling table having a cylinder support portion that is formed by a distal end opening side portion of the feed tube insert hole portion so as to support the cylinder; a connection member that is provided on the filling table at a location that is closer to the inside of the cylinder than the feed tube insert hole so as to connect a distal end of the feed tube to a paint channel that leads to a paint supply source; and a filling valve that is provided in the paint channel so as to carry out the supply of paint into the cartridge via the connection member and the stop of the supply.
Inside the filling valve, there are formed a paint supply passageway (paint supply channel) that connects to the paint supply source, and a drain passageway (waste liquid discharge channel) that connects to a drain tank. These two passageways are interlinked in communication via a linking passageway. When a paint is to be supplied into the paint cartridge, the drain passageway is shut off (closed) by a residual pressure relief valve that is provided in an intermediate portion of the drain passageway, so as to prevent part of the paint from flowing into the drain passageway (waste liquid discharge channel).
Japanese Patent Application Publication No. 2008-212869 (JP-A-2008-212869) proposes a paint filling apparatus (paint supply apparatus) that includes: a paint manifold having a plurality of collar valves; a cartridge attachment portion to which a paint cartridge is detachably attached; a paint filling channel (paint supply channel) that leads paint from the paint manifold into the paint cartridge when the paint cartridge is attached to the cartridge attachment portion; and a discharge channel (usage liquid discharge channel) that discharges paint and air residing in the paint filling channel to the outside. In the disclosed technology, a throttle device that has a plurality of elements that are disposed in line on the discharge channel is provided on the discharge channel (waste liquid discharge channel).
Japanese Patent Application Publication No. 2009-56382 (JP-A-2009-56382) discloses a technology relating to a paint filling apparatus (paint supply apparatus) that includes: a paint cartridge attachment portion that a paint cartridge is attachable to and detachable from; a paint supply channel that connects to the paint cartridge attached to the cartridge attachment portion; a first switching device (trigger valve) that switches between the linkage in communication between the paint supply channel and the paint cartridge attached to the cartridge attachment portion and the discontinuation of the linkage; a paint supply device that sends paint out into the paint supply channel; a discharge channel (waste liquid discharge channel) linked in communication with the paint supply channel; a second switching device that switches between a fully open state and a fully closed state of the discharge channel (waste liquid discharge channel); a paint sensor that detects paint in the discharge channel (waste liquid discharge channel); and a control device that is connected to the paint sensor and the second switching device, and that causes the discharge channel to assume the fully closed state by using the second switching device when the paint sensor detects the paint.
According to the technologies disclosed in Japanese Patent Application Publication No. 2000-176328 (JP-A-2000-176328), Japanese Patent Application Publication No. 2008-212869 (JP-A-2008-212869), and Japanese Patent Application Publication No. 2009-56382 (JP-A-2009-56382), the paint loss that occurs at the time of supplying paint into the paint cartridge can be minimized. However, in the technology disclosed in Japanese Patent Application Publication No. 2000-176328 (JP-A-2000-176328), the force that holds the residual pressure relief valve in the valve closure direction is composed of the urging force that is given by urging means, such as a coil spring provided within the filling valve, or the like, so that a part of the paint may sometimes flow into the drain passageway depending on increase in the back pressure that occurs in the paint supply channel. Thus, it is difficult to completely prevent the paint loss. Besides, neither Japanese Patent Application Publication No. 2008-212869 (JP-A-2008-212869) nor Japanese Patent Application Publication No. 2009-56382 (JP-A-2009-56382) shows a technology for preventing paint from flowing out into the waste liquid discharge channel linked in communication with the paint supply channel. Thus, a fundamental measure for reducing the paint loss has not been found.